Prior art of possible relevance includes U.S. Pat. No. 3,595,299 issued to Weishaupt et al and so-called single helix and double helix turbulators.
As is well known, the rate at which heat is exchanged in a heat exchanger through which a fluid, gaseous or liquid, is flowing is greatly affected by the nature of that flow, i.e., laminar, turbulant or transitional flow. Generally speaking, the more turbulant the flow, all other things being equal, the greater the rate of heat transfer. Stated another way, the higher the Reynolds number, the more rapid the rate of heat transfer.
However, in the design of heat exchangers, considerations other than solely that of high Reynolds numbers must be given great weight. High Reynolds numbers necessarily employ, all other things being equal, higher fluid velocities which in turn result in higher friction losses and therefore require more energy to generate.
A variety of other considerations frequently dictate a preference for relatively low Reynolds numbers of the heat exchange fluids which typically approach transitional or laminar zones. But, difficulties may be encountered when low Reynolds numbers are present in the heat exchange fluids in that slight changes in fluid flow introduced by small variations in pump performance or the like, including changes in pump speed may result in the fluid flow breaking down toward unstable transition flow or even laminar flow making it extremely difficult to obtain uniform heat transfer and/or desired rates of heat transfer.
In attempts to avoid such breakdown, the prior art has resorted to the use of so-called single or double helix turbulators in conduits housing fluids subject to a heat exchange process. Turbulators introduce turbulance into the fluid streams to maintain turbulant flow in conduits at Reynolds numbers whereat transition or laminar flow would occur without the presence of a turbulator. Such prior art turbulator structures as those identified above have been able to maintain turbulant flow heat transfer capability to relatively low Reynolds numbers but tend to allow fluid flow to break down toward unstable transition and/or laminar flow at Reynolds numbers frequently in the range of 1000-1500. Consequently, when using such devices, in order to sustain stable turbulant flow at low flow rates, resort has been made to multipass heat exchanger circuits which, of course, add expense to the heat exchange system.
Thus, there is a rear need for a turbulator that can extend the transition-laminar breakdown point to even lower Reynolds numbers to eliminate the need for multipass heat exchanger circuits or, at least, minimize the number of multipass circuits that are required in a given application.